The stock market has risen with breakneck speed this year, leaving many investors feeling paranoid rather than euphoric.

The Standard & Poor's 500 index was up 16.9 percent through Friday. That is its best start to a year since 1987, when it rose 18.7 percent during the comparable period. Later that year, on Oct. 19, the Dow Jones industrial average plummeted 508 points, or 22.61 percent, in a historic crash known as Black Monday.

Although the market dipped Monday, it is still up 16.8 percent year to date. And many investors feel that performance is not supported by the economy or corporate earnings.

Gross domestic product grew a modest 2.5 percent in the first quarter, following a scant 0.4 percent increase in the fourth quarter.

And although corporate earnings are at record highs, their growth rate leaves something to be desired.

With most companies in the S&P 500 having reported their first quarter results, their earnings per share are expected to be up 5.1 percent on average compared to the same quarter last year, according to S&P.

Unfortunately most of that growth has come from cost cutting and stock buybacks. When companies repurchase shares, which they have been doing a lot lately, their earnings per share rise even if their earnings have not.

Revenues -- a better indicator of demand for a company's product or services -- grew only 1.3 percent in the first quarter according to S&P. FactSet says they actually shrank 0.3 percent, but that was mainly due to a decline in the energy sector.

"The predominant reason for strong corporate earnings has been cost cutting," says Michael Cuggino, president of the Permanent Portfolio funds. "The next growth has to come from improving business conditions."

Earnings rebound

That won't happen fast. Analysts are expecting revenues and earnings will grow only 1.4 percent in the current quarter, says John Butters, senior earnings analyst with Norwalk-based FactSet. They are expecting a strong earnings rebound in the second half -- up 7.8 percent in the third quarter and 13.1 percent in the fourth.

If they are right, this year's rally will seem justified, but analysts are notorious for having overly optimistic longer-term forecasts.

Many analysts believe the market is moving mainly because most central banks have and will continue to reduce interest rates to a level that makes cash and other safe investments painfully unattractive.

Rottinghaus traces the current rally back to September, when the Federal Reserve announced it would try to keep rates low indefinitely with a third round of so-called quantitative easing. The only bumps in the market since then came "in the fall and late last year when we were dealing with sequestration," Rottinghaus said. "Once we got that off the table it was nonstop."

Like 1982

Many fear that when the Fed reverses course, the market will fall off its sugar high and crash.

He points out that when former Fed chief Paul Volcker roughly doubled the federal funds rate between August 1979 and January 1981, the market rose. It climbed again when his successor Alan Greenspan raised rates from mid-2004 through mid-2006.

From a technical standpoint, the market "looks a lot like 1982 when it broke out from 16 years of doldrums," Krsek says. "I was a rookie then, a lot of the older guys were skeptical. But from 1982 to 2000 the market went up by a factor of 14 times."

That said, Krsek and many others would not be surprised to see a short-term correction given the market's recent streak.

"While we don't see any imminent catalysts for big declines, we think fundamentals need time to catch up with stock prices and therefore expect some near-term consolidation," says Alexander Young, global equity strategist with S&P Capital IQ.

`Sell in May'

The S&P 500 has risen 61 out of 96 trading days this year. That ratio of up days to total trading days -- 64.2 percent -- is high by historical standards.

If you look at full years since 1950, the average percentage of up days was 52.9 percent and the highest was 62.3 percent in 1958, according to Jeffrey Hirsch, editor of the Stock Trader's Almanac and chief strategist of the Magnet AE Fund.

"I'm cautious and nervous as a rule, especially this time of year, especially after such a move," says Hirsch.

He notes that over the long term, the market tends to rise from November through April and to be "flat to down the rest of the year." This has given rise to the adage "sell in May and go away," which Hirsch says is a mistake because most people forget to come back in.

Granted, some individual stocks are looking bubbly. Electric-car maker Tesla Motors, which has a single model in production, is up 172 percent year to date and is now worth more than Fiat/Chrysler.

But on average, companies in the S&P 500 are trading at about 15 times this year's expected earnings, which is neither high nor low from a long-term perspective.

Rotblut notes that individual investors, who tend to get overly bullish near market tops, are also "right about average" in terms of their bearishness/bullishness, based on a survey his association does.

"I'm not seeing signs that anyone is being irrationally exuberant," Rotblut says. "You can make the argument that the macro environment does not support the rise in stock prices. The alternative is, what are you going to invest in?"